1. Field
Example embodiments relate to a metallocenyl dendrimer, an organic memory device using the metallocenyl dendrimer and a method for fabricating the organic memory device. Other example embodiments relate to a metallocenyl dendrimer composed of a dendrimer and metallocenes as redox species linked to the dendrimer, an organic memory device fabricated using the metallocenyl dendrimer with improved operating characteristics and improved non-volatility, and a method for fabricating the organic memory device.
2. Description of the Related Art
With the recent dramatic developments in digital communication technology, demand for a variety of memory devices has been increasing rapidly. Memory devices suitable for use in applications including, for example, portable computers and electronic devices, including mobile terminals, smart cards, electronic money, digital cameras, personal digital assistants, digital audio players and/or multimedia players, are required for retaining data in memory even when no power is being applied to the memory device, thereby tending to reduce the memory-related power consumption of the device. Conventional memory devices may include a bistable element that may be switched between a higher resistance state and a lower resistance state when a voltage is applied to the devices. Resistive memory devices are memories whose resistance is varied depending on an applied voltage and in which data is stored in response to variations in the resistance.
Chalcogenide materials, semiconductors and various types of oxides and nitrides are known to have resistive memory properties. Some organic materials are also found to have resistive memory properties. Of these resistive memory devices, organic memory devices may include an upper electrode, a lower electrode and a memory layer between the upper and lower electrodes, wherein the memory layer may be formed of an organic material and memory properties are realized by using bistability of resistance values obtained when a voltage is applied between the upper and lower electrodes. Next-generation organic memory devices ensure non-volatility, which is an advantage of conventional flash memories, and at the same time, overcome the disadvantages of undesirable processability, increased fabrication costs and decreased degree of integration.
For example, the related art discloses an organic memory device using 7,7,8,8-tetracyano-p-quinodimethane (CuTCNQ), which is an organometallic charge transfer complex compound. The related art also introduces a semiconductor device comprising an upper electrode, a lower electrode and an intermediate layer between the upper and lower electrodes wherein the intermediate layer is formed of a mixture of an ionic salt, e.g., NaCl or CsCl, and a conductive polymer.
The related art also suggests an organic memory device comprising organic active layers and a metal nanocluster applied between the organic active layers. However, this device has problems in that the yield of the device may be relatively low, the metal nanocluster may not be readily formed and the device may be reset at about 0 V, which may make the device actually unsuitable for use as a nonvolatile organic memory.
On the other hand, metallocenes and their derivatives are currently being investigated for their inherent electrical, optical and magnetic properties, for example, their ability to be oxidized to form mixed valent states. However, a major portion of research on metallocenes and their derivatives has been devoted to their use as fuel additives and polymerization catalysts. There hasn't been any research on the use of metallocenes and their derivatives as materials for active layers of organic memory devices.